#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <string.h>
#define STR_MAX 1000
void sort(char* str, int ret)
{
    for (int i = 0; i < ret; i++)
    {
        for (int j = 0; j < ret - i; j++)
        {
            if (str[j] > str[j + 1])
            {
                char tmp = str[j];
                str[j] = str[j + 1];
                str[j + 1] = tmp;
            }
        }
    }
}

int main()
{
    char str[STR_MAX];
    fgets(str, sizeof(str), stdin);
    int ret = strlen(str);
    sort(str, ret);
    for (int i = 0; i <= ret; i++)
    {
        if (str[i] != '\0' && str[i] != '\n')
        {
            printf("%c", str[i]);
        }
    }
    return 0;
}